NSDateFormatter bug

ampmBug.M

// dateString expected format: "2012-08-08 17:31:01 Etc/GMT"
// This value comes from our receipt-verification service,
// so it's independent of any of the user's settings
+(NSDate*)translateExpirePurchaseStringToDate: (NSString*)dateString {
    
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];

    // strip the ending
    NSString *purchaseDateString = [dateString stringByReplacingOccurrencesOfString:@" Etc/GMT" withString:@""];
    
    // set the gmt timezone just in case
    [dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
    
    // -- Here was my bug:
    // The purchaseDate value assignment below is nil when the user's 
    // preferences are: UK Calendar, London timezone with 24-hour time OFF.
    //
    // Having the user turn 24-hour time on in their phone's preferences
    // yielded an NSDate just fine. 
    // 
    // It wasn't what I'd expected, since the input value is totally
    // independent of the user's settings. :'(
    //
    [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];    
    NSDate *purchaseDate = [dateFormatter dateFromString:purchaseDateString];
    
    // 
    // ... do some other unrelated things
    //
    
    return purchaseDate;   
}